Banks and hedge funds that gamed Broward County's $90 million online tax lien auction at the expense of small investors will lose their edge this spring under new rules adopted by the county commission.

In recent years, some financial heavyweights had found a way to win most Broward tax liens by flooding the auction with bids from tens of thousands of shell companies. Mom and pop investors and other investment firms found themselves unable to compete.

The new rules aim to prevent companies from using multiple shell companies in auctions, restricting each individual or company to a single bid for each lien.

Broward County took action after a Sun Sentinel investigation published in May exposed the problem.

Commissioner Lois Wexler, who led the reform charge, said the revisions were "absolutely in the right direction."

The liens are placed on properties by local governments when taxpayers fall behind on their taxes. Each spring, the county then auctions off the liens to the private sector. Winning bidders pay the county the overdue tax and then are reimbursed -- with interest -- when the taxpayer finally settles up.

During the recession, tax liens became a more attractive investment for banks and hedge funds because Florida law guarantees at least a 5 percent return on obligations settled within a year. The ease of Florida's online system also enticed investors.

Some players statewide, however, found a way to manipulate the process and gain an advantage.

They used automated computer programs to obtain corporate taxpayer ID numbers from the IRS by the tens and hundreds of thousands. The ID numbers were assigned to shell companies, many with odd names such as Pork Chop Sandwiches or Yay for Tax Liens.

With the IDs, the banks and hedge funds could register tens of thousands of the companies as "sub-accounts" in many Florida online tax lien auctions. The online systems allowed the parent company to bid on behalf of all the related companies with a single keystroke.

The entities flooded the auctions with bids and won tie votes in random lottery draws because they had far more chances than the competitors.

In the 2013 tax lien auction, Broward had 219 primary bidders. Of those, 25 had registered about 2.4 million related "sub-accounts."

"The fairness and integrity of the Florida tax sales have been compromised," Gary Branse, director of tax certificates for the Miami-based Kislak Organization, told the Broward County Commission in early January, as it contemplated new rules.

Under Broward's new rules, similar to ones in place already in Palm Beach and Sarasota counties, bidders will not be allowed to create any related sub-accounts.

Participants will have to sign legal documents declaring that they are following the rules. The county will also put in place greater review mechanisms to police the auction, and is increasing deposits from $1,000 to $2,000 per bidder.

Palm Beach County Tax Collector Anne Gannon said her county had a successful auction last year under comparable restrictions. "It went well," she said.

Will the investment wizards eventually find a way around the constraints?

In an interview, Gadsden County Tax Collector W. Dale Summerford, a leading expert on the reform efforts, said: "I am not aware of any loopholes in the system at this point."

But Gannon predicted that some financial mastermind eventually will find a dodge, forcing the counties to take additional action.

She likened the online auctions to a chess game between regulators and big investors.